High frequency iron core



Filed Dec. 12, 1939 iNVENTOR HERMANN ST/ER ATTORNEY Patented Jan. 6,1942 HIGH FREQUENCY IRON CORE Hermann Stier, Berlin, Germany, asslgnorto -Telefnnken Gesellschaft fiir Drahtlose Telegraphic in. b. 11.,Berlin, Germany, a corporation of Germany Application December 12, 1939,Serial No. 308,813 In Germany November 25, 1938 2 Claims.

when mass cores are used for high frequency coils the core aside frombeing permeated by magnetic lines of force is also permeated by electriclines of force. In the figure wherein the coil is designated by Sp andthe core by K, such an electric field line is shown in dotted lines.

Since the dielectric constant of the mass core (pressed material orsprayed material) is very high and furthermore has often a very hightemperature coefilcient, the dielectric behavior of the mass core isfound to be an inconvient feature when the core is to serve fordetermining the frequency particularly in the case of short waves. Itwould as such be conceivable to shield the core against electric fieldlines by means of an electrically conducting sheet metal mantle but inthis case an additional element of the structure is required, namely,the shielding mantle.

In accordance with the invention in a high frequency iron coreconsisting of finely distributed iron powder and a binder, anelectrically semi-conducting binding means is employed. It is possiblefor instance to add carbon in an extremely fine distribution of the typeused for making resistance layers.

It in using the invention the conductivity becomes essentiallygreaterthan the wattless conduction value of the capacity which isformed by the iron core as the dielectric, yet not as high asconductivity of the iron, the dielectric behavior is no longer ofimportance. Hence, dielectric losses occur no longer. The upper limitfor the value of the conduction lies in the additional damping which iscaused in the core by the eddy currents due to the conduction. Thislimit is determined by the respectively prevailing frequency range anddielectric constant of the material and can be maintained withinreasonable limits. Hence, the conductivity of the entire iron core isgiven a value such that the eddy losses are still permissible and thedielectric losses are diminished in view of the conducting shunt.

Moreover, it will be sufilcient if only the exterior layer of the coreis devised in the manner according to the invention. But in this casethe making of the core meets with difiiculties.

I claim:

1. A core for a high frequency inductance device composed of compressedfinely divided magnetic material mixed with a semi-conducting binder,said binder being composed of insulation material mixed with finelydivided carbon.

2. A core for a high frequency inductance device composed of finelydivided iron mixed with a binder which has finely divided carbo'ndispersed throughout it.

- HERMANN STIER.

